MINERAL SEPARATION
liners had a longer wear life than the existing hydrocyclones . The Cavex 800CVX hydrocyclones produced a finer grind size ( 3.1 % + 100 mesh ) compared with the baseline 762 mm hydrocyclones – resulting in a better bulk flotation for copper / molybdenum recovery . The Cavex hydrocyclones also produced a lower fines bypass / water recovery to underflow and a lower overflow density , which resulted in better classification efficiency .
Spiral satisfaction
Using its extensive in-house testing facility for material from a South Africa manganese producer , Multotec recently defined a solution that , it says , can upgrade the quality of saleable concentrate while reducing the content of manganese in tailings .
According to Faan Borman , Technology Manager : Research and Development at Multotec ’ s technology division , the customer had specific targets they wanted to achieve . These targets looked to optimise revenue from recovered minerals and improve environmental performance , as a level of more than 10 % Mn in the tailings would require the dump to be classified as hazardous .
“ The test work we conducted was to improve recovery of ultra-fine material from the thickener underflow ,” Borman said . “ The financial benefit of better recoveries is to produce a richer concentrate , but it is also to reduce the metal content in tailings – so that it would not be regarded as hazardous waste .”
Two sets of test work were designed and conducted . In the first set , stockpile material with a metal grade of 16 % Mn was tested using Multotec ’ s UX7 ultra-fine spiral concentrator for the roughing and scavenging phases , while its SC21 five-turn spiral was used for the cleaning stage . This allowed the target saleable grade of 32 % Mn to be achieved , Borman says , but work was still required to reach the tailings target grade .
“ This required some out-of-the-box thinking for the second set of tests , where we ran the material over the WHIMS with a vertical ring ,” he says . “ At the highest intensity , this was able to downgrade the spiral tailings material from 13 % to 14 % right down to 7 % manganese – a significant improvement .”
Given the higher cost of applying WHIMS technology , the testing procedure using spirals was able to remove gangue minerals and reduce the volume of bulk material before being treated by the WHIMS .
“ Another benefit of this process was that about a third of the material sent to the WHIMS in this process could be returned to the spiral circuit for further upgrade to meet specifications ,” Borman said . “ This considerably reduces tailings volumes , potentially cutting down the footprint of the tailings storage facility and extending its lifespan .”
Borman says the cost of managing tailings facilities in a compliant manner , and the tightening regulations and policies on tailings dams , are encouraging operators to look at reprocessing . Technology improvements in metal recovery over the years now makes these retreatment efforts commercially attractive .
“ We have had considerable success in applying the spirals together with the WHIMS , as it is key to ensure sufficient bulk reduction up front ,” he said . “ The process can be applied across a range of commodities , and we have also seen good results in minerals including chrome , iron ore , lithium and mineral sands .”
Bibiani boosts competence , automation
An “ up-to-date ” Knelson 6G concentrator and a Gekko ILR ( InLine Leach Reactor ) has helped Asante Gold upgrade its gravity recovery circuit at the Bibiani gold mine in Ghana to “ model year 2021 ” level of competence and automation , the Vancouver-based company said earlier this year .
Asante , which acquired the mine in 2021 from Resolute Mining , has a plan to bring Bibiani into production in the September quarter of 2022 , stating in February that open-pit mining had commenced and the process plant refurbishment work was more than 60 % complete .